Connection for rigid coaxial transmission line

ABSTRACT

This disclosure relates to connectors used in joining rigid inner sections of high energy conducting coaxial transmission lines and distinguishes over the existing state of the art by providing a one contact surface joint which, while permitting the desired axial expansion and contraction movements inherent in those structures, avoids the well known problem of galling dust accumulations by including as an integral part of the connector, a receptacle for capturing this dust and associated particle matter.

United States Patent [191 11] 3,818,421 Kru er June 18 1974 CONNECTIONFOR RIGID COAXIAL 3,432,779 3/l969 Sewell 339/177 R TRANSMISSION LINE[76] Inventor: Jack L. Kruger, Goffstown, NH. Examiner-198cm y f [22] Hd Aug 3 1973 Attorney, Agent, or Fzrm--G0ode & Chittick ,7 [21] Appl No390 46 ABSTRACT Related US. Application Data I [63] Continuation of SerNo 242 543 A r 10 1972 Th s disclosure relates to connectors used inoining abandoned p rigid inner sections of high energy conductingcoaxial transmission lines and distinguishes over the existing [52] U SCl 339/177 R 339/255 R state of the art by providing a one contactsurface [51] h 13/16 joint which, while permitting the desired axialexpan- [58] Fie'ld 253 sion and contraction movements inherent in those3 structures, avoids the well known problem of galling dustaccumulations by including as an integral part of [56] References Citedthe connector, a receptacle for capturing this dust and UNITED STATESPATENTS Sewell 339/177 R associated particle matter.

7 Claims, 3 Drawing Figures CONNECTION FOR RIGID COAXIAL TRANSMISSIONLINE CROSS REFERENCE TO RELATED APPLICATIONS This application is acontinuation of the application ofJack L. Kruger Ser. No. 242,543 filedApr. l0, I972, for Connector for Rigid Coaxial Transmission Line, andnow abandoned.

BACKGROUND OF THE INVENTION This invention relates generally to rigid,high-energy carrying co-axial transmission line equipment of the typeemployed in transmitting energy to a radio or television antenna. Moreparticularly, this invention relates to a novel connector for joininglinear sections of such inner conductor, these connectors sometimesbeing referred to as bullets.

Antennas used in audio-visual broadcasting are generally mounted on topof high towers and may be spaced from a transmitter by as much as 300 to2,000 feet. A coaxial transmission line connects the antenna andtransmitter. Such coaxial transmission lines are generally comprised ofassembled lengths of inner and outer tubular conductors held in spacedapart concentric relation from one another by a series of nonconductivecylindrical spacers positioned at'regular intervals along the length ofthe inner transmission line at the connecting joints.

To date virtually all manufacturers of coaxial transmission lines haveused the well known connector comprised of a tubular cylinder withlongitudinal slots at one end to provide a series of flexible leafs orsegments. These prior art connectors, usually of silver-plated brass,are typically used to join adjacent lengths of inner conductor in acoaxial transmission line. The problem incurred when using this type ofconnector is the wear that takes place between the connector and thetubular object it is mated to due to differential expansion between theouter conductor and inner conductor which is 0.2 inches of travel per 20foot length. This wear is commonly referred to in the industry as bulletgalling. Manufacturers of coaxial transmission line have tried variousmethods to eliminate connector galling. The reason for concern over thisproblem is that as the connector wears (galls) in its day to dayexpansion cycle it produces metal filings which can fall and collect onthe teflon insulator maintaining the connectors position and locking itinto the transmission line. This occurrence over a period of time cancreate a path of metal dust to ground (from the inner conductor to theouter conductor) which greatly diminishes the voltage carryingcapability of the transmission line. Depending on the power beingapplied to the transmission line the ultimate result of this conditionis loss of signal or the eventual breakdown and burnout of thetransmission line.

As stated previously the basic construction materials used by mostmanufacturers in the industry are silver plated brass or silver platedberyllium copper. Some manufacturers have even put on a baked-on carbonbase material on the contacting finger surfaces of the connector tolubricate and minimize the galling effect. This coating does not enhancethe electrical conductuity of the connector. When these coatings orplatings wear off, as they eventually do, the contacting or conductingsurface is then through brass or beryllium copper which has only 1/6 ofthe conducting power of copper. This condition in a high powertransmission line generates heat due to the resistance of the contactingsurface and can only aid the transmission line on its path toself-destruction.

Some of the problems related to the multi-fingered connector of theprior art are that during assembly and erection of the transmission linein the field, one or more of the connector fingers would be easilybroken off or otherwise damaged. This, in turn, led the industry todevelop so-called anti-split devices which, in effect, wereself-aligning fixtures at the end of the connector. Another seriousdisadvantage of the multi-fingered connector is that even though it ismachined and formed from a precision round piece of material, when thelengthwise fingers or slots are formed, and the material is stressrelieved, it is no longer accurately round, thus, when inserted orconnected to the corresponding round female counterpart, the electricalcontact area around the periphery of the finger connector occurs only atintermittent high spots.

SUMMARY OF THE INVENTION My invention overcomes these deficiencies byproviding a novel expansion joint for use with the inner conductor of acoaxial transmission line in which one end of a conductor segmentcarries a rigid plug carrying a coiled spring adapted for insertion intoa corresponding receptacle or cup member secured to the linearlyadjacent end of another conductor segment. This cup member catches andretains therein any metallic particles or galling dust generated by therelative movement of adjacent conductor segments due to expansion andcontraction motion. My invention further provides a novel retaining ringsurrounding the coiled spring carried by the plug portion whereby toprevent its dis- Iodgement from its annular seat on the plug.

It is, accordingly, among the various objects of this invention toprovide a coaxial transmission line connector which has only onecontacting surface between adjacent sections of conductor.

It is a further object of this invention to provide an expansion jointfor a coaxial transmission line which seals each end of adjacentsections of conductor, thus, preventing dust or conductive chips fromfalling out of the inner conductor during its erection assembly.

A still further object of this invention is to provide a coaxialtransmission line connector which eliminates the prior art form offingers.

Another and further object of this invention is to provide a receptaclefor. capturing and retaining all particles and dust generated due to theexpansion and contraction movements between joined conductor segments.

An important feature of this invention is that the novel design of theconnector members permits semiskilled workers to erect coaxialtransmission line with a minimum of risk of damage thereto duringerection.

Another feature of this invention is that the total conducting contactsurface between connected portions of conductors is substantiallygreater than the contact available with the current state of the artmulti-finger bullet" or connector.

These and other objects and features will become more apparent from thefollowing description when taken in conjuction with the appendeddrawings in which:

FIG. 1 illustrates an elevation view of my connector in fully assembledcondition;

FIG. 2 illustrates a vertical cross-sectional view of FIG. 1 taken online 22 thereof; and

FIG. 3 illustrates an exploded view of the components illustrated inFIGS. 1 and 2.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now with greaterparticularity to the drawings, there is shown in the drawings variousviews of my novel inner conductor connector (i.e., bullet) comprised ofa plug member 11 permanently connected into the bottom end of aconductor segment 9 and adapted for insertion and retention into areceptacle or cup member 12 which is permanently connected to the topend of the segment 9 therebelow. Both plug 11 and receptacle 12,fabricated of copper or other suitable conductive material, are securelyattached into their respective adjoining ends of adjacent conductorsegments 9, generally by means of silver soldering or brazing. For thispurpose, there is provided on the upper end of the plug and the lowerend of the receptacle an annular recess 13 around which is wrapped alength of sliver solder (not shown). Prior to assembly of the segments,these end portions with the silver solder thereabout are inserted intothe ends of the respective conductor segments 9 until the lower end ofthe upper conductor abuts the corresponding annular shoulder 14 on theplug 11 and the upper end of the lower conductor abuts the correspondingannular shoulder 14 on the receptacle 12. The plug and receptacle arethen subjectedto the necessary heating to cause the solder to flow. Itshould be apparent that the inside diameter of each conductor segment 9is sized to slidably fit over the end of plug 11 and receptacle 12.

The lower end of plug 11 is provided with an annular recess 15 toreceive and accommodate a coiled spring 16. This is a springcharacterized by two broad flat surfaces with rounded ends. The wireforming the spring is wound in a continuous form and generally silverplated for good electrical conductivity. The depth of recess 15 is soproportioned that when spring 16 is carried therein, the outsidediameter of the spring is slightly larger than the inside diameter ofrecess 17 in receptacle 12. Thus, when plug 11 with spring 16 isinserted into recess 17, the spring will resiliently yield so as topermit its accommodation within the dimensional confines of recess 17,thus providing a firm contact against both the plug 11 and thereceptacle 12 while at the same time conforming to any eccentricity orout-ofround condition of the recess 17.

There is also provided on receptacle member 12 an annular recess 18 foraccommodating an electrically non-conducting plastic spacer 19, referredto hereinabove. In accord with conventional practice, the outerperiphery of the spacer 19 is attached to the related outer tubularconductor. The spacer carries the weight of each segment 9.

Frequently, when adjoining segments of inner conductor 9 are beingassembled in the field, since the outside diameter of the coiled spring16 is larger than the inside diameter of recess 17, careless assemblyprocedures will often pop" or push the spring out of its recess l5, andeither severely deform or damage it, thus resulting in poor andincomplete electrical contact between the joined sections. In order toeliminate this possibility, I provide on plug 11 an electricallynonconductive retaining ring or slip ring 20 made of suitable plastic,for example, teflon. This ring 20, as seen in the cross-sectional viewof FIG. 2, is annularly shaped with a uniform outside diameter. Theinternal configuration, however, is stepped, i.e., the surface 21 isdimensioned so as to be slidable over the surface of plug 11. See FIG.3. Surface 22 is of slightly larger diameter so as to clear the outsidediameter of spring 16 and be slidable thereover. A chamfered edge 23 isprovided on the bottom of plug 11 to eliminate the upper edge portionsof receptacle 12 from catching thereon during assembly. Thus, when plug11 is inserted into recess 17 of receptacle 12, surface 22 of slip ring20 initially surrounds spring 16 thereby preventing its dislodgementfrom its annular seat 15, as shown in the FIG. 3 view and compellingspring 16 to assume its correct position within recess 17. As the upperend of receptacle 12 passes over spring 16, the ring 20 is engaged andpushed upward along plug 11 to its final position shown in FIGS. 1 and2. Alternatively, it may be desirable prior to assembly of this joint tolower the position of slip ring 20 from that shown in FIG. 3, so thatits inner surface 21 actually covers spring 15 in compressive relationand with the skirt portion 22 extending below the bottom of the spring.

It should, accordingly, now be apparent in light of the foregoingdisclosure that I have significantly improved on the prior art form ofinner conductor connectors for coaxial transmission lines by providingonly one electrically contacting surface between joined conductorsegments using a coiled spring in a novel manner. This spring and itscontacting receptacle surface are the only relatively moving portionsgenerating dust or particulate matter, and this dust and matter arecaptivated below plug 11 in the recess of the receptacle 12 where itwill have no deleterious effect on the performance of the conductorline.

Further, by using the plastic slip ring 20 over spring 16, it not onlyenables unskilled personnel to easily assemble a rigid conductor line inthe field, but more importantly, the plastic insert itself cancels outthe inductance presented by the dimensional change in size of thediameter of plug 11 from the diameter of the remaining transmission line9; thus, by adding a plastic dielectric in this region of inductance onthe plug, capacitance is effectively added, thus canceling out theelectrical reflection caused by this condition.

A further feature which should now also be apparent is that because Iuse only one contacting surface between adjoining conductor segments,there is only onehalf the junction resistance (i.e., insertion loss) andthis, accordingly, permits better thermal conductivity. Because the linenow only has one-half of the conventional connections, this results inthe elimination of damaging hot-spots.

The connector design herein disclosed enables this device to be usedwith both thin wall (i.e., 0.025 inches wall thickness) or thick wall(i.e., 0.040 inches wall thickness) tubing. Conventionally availableconnectors should generally be used with either one or the other, butcannot be interchanged without the possibility of severely affecting theelectrical performance of the line.

When in the claims, the terms bottom end and top end of the conductorsegments are used, it will be appreciated that there will also be agenerally horizontal portion of the transmission line running from thetransmitter to the tower. Thus the bottom end of each segment is the endnearer the transmitter, whether the segment be in vertical or horizontalposition.

It will be understood that various changes in the details, materials andarrangement of parts which have been herein illustrated in order toexplain the nature of the invention may be made by those skilled in theart within the principle and scope of the appended claims.

1 claim:

1. A connector for joining linear sections of inner conductor of acoaxial transmission line, comprising the combination of:

a. a plug means adapted to be secured into the bottom end of an innerconductor of a coaxial transmission line;

b. a receptacle closed at its bottom and adapted to be secured into thetop end of an adjoining conductor section therebelow, for receiving saidplug means;

c. an annular recess around the portion of said plug means which isinsertableinto said receptacle; and

d. resiliently yieldable electrically conductive means carried in saidannular recess for making electrical contact between said plug andreceptacle.

2. The combination set forth in claim 1 wherein said resilientlyyieldable conductive means comprises a coiled spring.

3. The combination set forth in claim 2 further comprising a retainingring slidably carried on said plug means to cover at least a portion ofsaid coiled spring to retain it in position in said recess duringinsertion of the said plug and spring into said receptacle.

4. An inner conductor of a coaxial transmission line comprising thecombination of:

a. a plurality of linearly joined conductor segments;

wherein each joined conductor segment comprises:

b. an electrically conductive tube member;

c. a plug means secured into and closing the bottom end of said tubemember d. a receptacle means secured into and closing the top end ofsaid tube member and adapted to receive the plug means of a linearlyadjacent conductor segment thereabove, said receptacle closed at itsbottom end; and

e. a resilient and conductive spring means carried on that portion ofsaid plug means which is insertable into said receptacle forestablishing and maintaining electrical conductivity through joinedconductor segments.

5. The structure set forth in claim 4 wherein each said plug meansslidably carries a retaining ring to retain said spring means inposition during insertion into its receiving receptacle.

6. Means for electrically connecting in aligned relation adjacent endsof the inner conductors of a coaxial transmission line, said meanscomprising,

a plug permanently secured to the lower end of one segment of saidconductors,

an upwardly facing receptacle closed at its bottom and having a lowerbody part permanently secured to the upper end of the next adjacentsegment of said conductors, said receptacle shaped to receive thereinsaid plug in close sliding engagement,

a first annular recess around the portion of said plug means which isinsertable into said receptacle,

resiliently yieldable electrical conductive means carried in said firstannular recess for making positive electrical contact between said plugand receptacle,

a second annular recess in said lower body part below the said bottom ofsaid receptacle and above said upper end of the segment to which saidbody part is attached, a circular load carrying spacer mounted in andabout said second annular recess for supporting the inner conductordepending therefrom,

whereby following assembly of said inner conductors between thetransmitter and antenna, there will be only one non-permanent andslidable connection per segment of conductor and said non-permanentconnection will be on the antenna side of said spacer.

7. The combination set forth in claim 6, said resiliently yieldableelectrically conductive means comprising a coiled spring and a retainingring slidably carried on said plug to cover at least a portion of saidcoiled spring to retain it in position in said first recess duringinsertion of said plug and spring into said receptacle.

1. A connector for joining linear sections of inner conductor of acoaxial transmission line, comprising the combination of: a. a plugmeans adapted to be secured into the bottom end of an inner conductor ofa coaxial transmission line; b. a receptacle closed at its bottom andadapted to be secured into the top end of an adjoining conductor sectiontherebelow, for receiving said plug means; c. an annular recess aroundthe portion of said plug means which is insertable into said receptacle;and d. resiliently yieldable electrically conductive means carried insaid annular recess for making electrical contact between said plug andreceptacle.
 2. The combination set forth in claim 1 wherein saidresiliently yieldable conductive means comprises a coiled spring.
 3. Thecombination set forth in claim 2 further comprising a retaining ringslidably carried on said plug means to cover at least a portion of saidcoiled spring to retain it in position in said recess during insertionof the said plug and spring into said receptAcle.
 4. An inner conductorof a coaxial transmission line comprising the combination of: a. aplurality of linearly joined conductor segments; wherein each joinedconductor segment comprises: b. an electrically conductive tube member;c. a plug means secured into and closing the bottom end of said tubemember d. a receptacle means secured into and closing the top end ofsaid tube member and adapted to receive the plug means of a linearlyadjacent conductor segment thereabove, said receptacle closed at itsbottom end; and e. a resilient and conductive spring means carried onthat portion of said plug means which is insertable into said receptaclefor establishing and maintaining electrical conductivity through joinedconductor segments.
 5. The structure set forth in claim 4 wherein eachsaid plug means slidably carries a retaining ring to retain said springmeans in position during insertion into its receiving receptacle. 6.Means for electrically connecting in aligned relation adjacent ends ofthe inner conductors of a coaxial transmission line, said meanscomprising, a plug permanently secured to the lower end of one segmentof said conductors, an upwardly facing receptacle closed at its bottomand having a lower body part permanently secured to the upper end of thenext adjacent segment of said conductors, said receptacle shaped toreceive therein said plug in close sliding engagement, a first annularrecess around the portion of said plug means which is insertable intosaid receptacle, resiliently yieldable electrical conductive meanscarried in said first annular recess for making positive electricalcontact between said plug and receptacle, a second annular recess insaid lower body part below the said bottom of said receptacle and abovesaid upper end of the segment to which said body part is attached, acircular load carrying spacer mounted in and about said second annularrecess for supporting the inner conductor depending therefrom, wherebyfollowing assembly of said inner conductors between the transmitter andantenna, there will be only one non-permanent and slidable connectionper segment of conductor and said non-permanent connection will be onthe antenna side of said spacer.
 7. The combination set forth in claim6, said resiliently yieldable electrically conductive means comprising acoiled spring and a retaining ring slidably carried on said plug tocover at least a portion of said coiled spring to retain it in positionin said first recess during insertion of said plug and spring into saidreceptacle.